A Very Old, Rare and Strange Mineral from our Early Solar System, near Mercury

Incredibly rare and rich with the mineral enstatite (MgSiO3) and a profile that resembles the planet Mercury. Enstatite is one of the few silicate minerals that have been observed in crystalline form outside the Solar System, particularly around evolved stars and planetary nebulae such as NGC 6302. Enstatite is thought to be one of the early stages for the formation of crystalline silicates in space.

NWA 10519 Enstatite achondrite (ungrouped)
Found 2015 in Mauritania
480 gm, 10” x 8” x 4mm
An enstatite-rich achondrite that is ungrouped with any other meteorite.

“Aubrites must have formed in a very unique part of the solar nebula, possibly within 1 AU of the Sun. While of the 27 aubrites, 15 are fragmental breccias, their ingredients are clearly of igneous origin and formed by melting and fractional crystallization, possibly of a magma ocean. Age dates suggest that the aubrites formed very early in the history of the solar system, within a few million years of CAI formation, and that the heat sources for heating and melting of their parent bodies were, most likely, short-lived radionuclides such as Al and, perhaps, Fe. Finally, attention has been drawn to the surface composition of Mercury of low bulk FeO and of nearly FeO-free enstatite. Meteoriticists should be alert to the potential discovery of a genuine meteorite from Mercury which, superficially, should resemble aubrites.” — from Geochemistry 2010

From the Meterorolical Bulletin for NWA 10519:
“a brecciated texture dominated by sub-angular to rounded dark-green to tan metal-silicate clasts, separated by an anastomosing network of metal veins. Electron microprobe analysis shows the silicates are enstatite, diopside, and albitic plagioclase, with minor silica. This meteorite is distinguished from enstatite meteorites by the lack of Si in metal and the low Ti content of troilite.”

Recent work on the theory of formation: “Although various scenarios of formation are proposed to explain petrogenesis of these ungrouped rocks, there is no consensus achieved so far. Noble gas signatures suggest that they are rather primitive achondrites that formed as residue after partial melting or recrystallized partial or complete melts. Currently, the most widely accepted interpretation is that these rocks were formed by crystallization of impact melt and therefore represent impact melt rocks or impact melt breccias. None of the scenarios, however, offers full, unequivocal explanation of how the texture was created and, as a consequence, what is the petrogenesis of these rocks.” — from Meteoritics and Planetary Science 2019

A small Near-Earth object, (3103) Eger, is also often suggested as the parent body of the aubrites.